package com.hmdp.utils;


import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;
import org.yaml.snakeyaml.events.Event;

import java.time.Instant;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Component
@Slf4j
public class CacheClient {

    private static    StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }
    public void set(String key, Object value, Long time , TimeUnit unit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value),time,unit);
    }
    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit){
        //设置逻辑过期
        RedisData redisData=new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入Redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }
    //缓存穿透的解决方案 空值，布隆
    public <R,ID> R queryWithPassThrough(
            String keyPrefix, ID id , Class<R> type, Function<ID,R> dbFallback,Long time, TimeUnit unit){
        String key=keyPrefix + id;
        //从redis查缓存
        String json= stringRedisTemplate.opsForValue().get(key);
        //判断是否存在
        if(StrUtil.isNotBlank(json)){
            //存在，直接返回
            return JSONUtil.toBean(json, type);
        }
        //命中空值
        if(json!=null){
            //返回错误信息
            return null;
        }
        //不存在，根据id查询数据库
        R r= dbFallback.apply(id);
        //不存在，返回错误
        if(r==null){
            //设置返回空值
            stringRedisTemplate.opsForValue().set(key, "",CACHE_NULL_TTL, TimeUnit.MINUTES);

            return null;
        }
        //存在，写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(r),CACHE_SHOP_TTL, TimeUnit.MINUTES);

        this.set(key,r,time,unit);
        //返回
        return r;
    }


    //逻辑过期了热点数据缓存击穿


    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    public <R,ID> R queryWithLogicalExpire(
            String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit){
        //缓存穿透的解决方案
        String key=keyPrefix + id;
        //从redis查缓存
        String shopJson= stringRedisTemplate.opsForValue().get(key);
        //判断是否存在
        if(StrUtil.isNotBlank(shopJson)){
            //存在，直接返回
            return null;
        }
        //4.命中，需要先把json反序列化为对象
        RedisData redisData=JSONUtil.toBean(shopJson,RedisData.class);
        R r=JSONUtil.toBean((JSONObject) redisData.getData(),type);
        LocalDateTime expireTime=redisData.getExpireTime();
        //5.判断是否存在过期
        if(expireTime.isAfter(LocalDateTime.now())){
            //5.1未过期
            return r;
        }
        //6.已经过期
        //缓存重建
        //获取互斥锁
        String lockKey=LOCK_SHOP_KEY+id;
        boolean isLocked=tryLock(lockKey);
        //判断是否获取成功
        if(isLocked){
            //成功，开启独立线程，实现缓存建立
            CACHE_REBUILD_EXECUTOR.submit(()->{
                try {
                    //创建这个缓存(先查数据库，再键redis)
                  R r1=dbFallback.apply(id);
                  //写入
                    this.setWithLogicalExpire(key,r1,time,unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unlock(lockKey);
                }
            });
        }
        //6.4返回过期的商铺信息
        return r;
    }
    //锁
    public static boolean tryLock(String key){
        Boolean flag=stringRedisTemplate.opsForValue().setIfAbsent(key, "1",10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    public static void unlock(String key){
        stringRedisTemplate.delete(key);
    }
}
